London has been battered by 50mph winds that have felled trees and caused travel chaos. Powerful gusts swept across the capital as the Met Office issued a yellow "be aware" weather alert for most of the country.

For the past couple of thousand years, Hercules has been best known for his 12 Labours: whacking the Nemean lion, topping the nine-headed Lernaean hydra, cleaning out the Augean stables, all that. Here, though, he strikes out in a new direction.

In this adaptation, based on Steve Moore’s comic-book series The Thracian Wars, we whizz through those Labours in a prologue. Now Hercules is a disillusioned mercenary, a freelance enforcer who has teamed up with a cool posse of warriors for hire to whoever pays best. Maybe he’s a demi-god, the son of Zeus and the mortal Alcmene — or maybe that’s just a story put about to impress his enemies?

We meet the gang as they dispatch a bunch of grungy pirates. Hercules is Dwayne “The Rock” Johnson, the former professional wrestler of part-Samoan descent, 6ft 5ins tall and weighing in at 260lb, exactly the man to have played the giant Jack Reacher instead of Tom Cruise. The Rock has an incredible blocky physique, huge veins standing out on his colossal biceps, just right for Hercules — actually, a pretty good match for the antique Farnese Hercules statue, though this being a 12A, we don’t get quite the full package that the Romans enjoyed.

Unfortunately, The Rock doesn’t have much on top these days, while Hercules is well-known to have boasted a full head of curly hair, so our hero has been supplied with long, hippyish — almost Neil from The Young Ones — locks, plus a fine beard and moustache, all artistically made, it seems, from the finest yak pubic hair, the go-to, no-expenses-spared material in these circs. Disconcerting — but under the beaver he’s still The Rock, massive and impassive, great at bone-crunching, maybe not so convincing when attempting a look of inner sorrow — but who cares?

His sidekicks include a wisecracking seer, Amphiaraus, played by campy 71-year-old Ian McShane, Lovejoy as was, whose weapon of choice is a big spear; Autolycus, played by hunky Rufus Sewell, fresh from Abraham Lincoln: Vampire Hunter, who favours little throwing knives; Tydeus, a mute axe-twirling madman, played by Norwegian Aksel Hennie; his loquacious nephew Iolaus (Reece Ritchie), who does Hercules’s PR for him but yearns to get stuck in too; and, most glamorously, Amazonian Atalanta, played by another Norwegian hottie, Ingrid Bolsø Berdal, in a sports bra and miniskirt, who favours the bow and arrow. It’s the A-Team! From ancient Greece.

Off they go to fight for Lord Cotys of Thrace (74-year-old John Hurt, doing that queeny voice and sarky intonation to the max), who says his lands are threatened by dark forces, probably including massed centaurs, under the leadership of sorcerer Rhesus (another Norwegian, Tobias Santelmann).

So Hercules and his pals, assisted by the amateurish Thracians, fight a hectic battle against hordes of tattooed savages, only just seeing them off with some sensational charioteering. Then there’s a training montage, a bit like Rocky, only with more of an emphasis on shield-wall discipline. In the next pitched battle, the Thracians do much better, while Hercules totals Rhesus’s chariot all by himself in best Fast & Furious style, not to mention strategically deploying the certificate’s one permitted swear word: “Fucking centaurs!”

They’ve won! But Lord Cotys has strung them along — and, what’s more, he’s in league with another supremely dodgy British thesp, Joseph Fiennes, aka King Eurystheus of Athens, a right ponce who has some bad history with Hercules that poor Herc keeps having horrible flashbacks about…

Such a shame our hero didn’t click that Cotys wasn’t playing fair earlier — sometimes a light seasoning of brains helps the brawn, doesn’t it? Now they have yet another battle to fight — and this time, Hercules is only going to win if he can really believe in himself, apparently a prerequisite in mythological as well as modern times. Message: “You don’t need to be a demigod to be a hero — you just need to believe!” Could be any one of us, really, tearing apart wolves with our bare hands.

Hercules is directed by Brett Ratner (Money Talks, Rush Hour, the Red Dragon remake, and X-Men: The Last Stand), not previously a name much rated for action movies. Hercules was shown to reviewers only at the last minute this week, a tactic studios adopt whenever they fear any early word on a film is going to be negative. But they were being over-cautious. On its own terms, Hercules delivers pretty well.

It’s essentially three giant battles, loosely connected by an uncomplicated plot — and those battles are well staged and well filmed, an involving combination of huge vistas, enormous numbers of troops that would have delighted Cecil B DeMille, and with a coherent depiction of specific combat, so that you have some sense of both how the overall fight is going and the perils and victories of individuals within it. It’s all in scale, not speeded up or slowed down, nor is the camera pointlessly whipped about, and it’s impressively violent without being too gory (Hercules favours mighty but simple clubbing — so refreshing). That all sounds like the most basic rules for making action sequences exciting and intelligible but it’s beyond many directors (remember Darren Aronofsky’s muddly battle scenes in Noah?).

Moreover, the decision to make Hercules only ambiguously divine — perhaps not actually a superhero at all — also pays off. The Rock isn’t CGI’d into nonsense and despite being genuinely a giant among men, he seems, as one of his enemies remarks in surprise, almost normal in stature. His struggles are the more convincing for it.

Maybe you really need to be a 12-year-old boy to be absolutely thrilled by Hercules but then lots of us know one, inside or out.